Details on .MSI files

I am looking for some detailed info on .MSI files. What exactly are they comprised of? What is actually the raw format of them? Where is the XML and the binary? What utilities are there for creating them? editing them? basically I really want to learn the deep and dirty of .MSI .

I have done searches in this forum and on Google and have thus far been unsuccesful. I NEED YOUR HELP. Anything that you might know/understand of them would be greatly appreciated. Any links with info etc.....

Thank you
Zev

Common, I know some of you understand/know something about these. I really have been fairly unsuccesful in finding any info on them. PLEASE HELP!

Thanks

Zev